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A229687
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Odd squares whose binary reversal is also a square.
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3
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1, 9, 20457529, 143784081, 331130809, 4365905625, 5216450625, 20074072489, 1193532215121, 10036851273801, 36014509461681, 38767247532225, 41413201925481, 155991531977649, 320642706437001, 2543173099393689, 2696589987547401, 4665141483989281, 87463589042698969
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OFFSET
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1,2
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COMMENTS
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The sequence of binary reversals that are squares is a permutation of a(n), it begins: 1, 9, 20457529, 143784081, 331130809, 5216450625, 4365905625, 20074072489, 1193532215121, 10036851273801, 38767247532225, 36014509461681, ...
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LINKS
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FORMULA
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PROG
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(C)
#include <stdio.h>
#include <math.h>
int main() {
unsigned long long n, t, r, sr;
for (n=1; n<(1ULL<<32); n+=2) {
t = n*n;
r = 0;
while (t) r = r*2+(t&1), t >>= 1;
sr = sqrt(r);
if (sr*sr==r) printf("%llu, ", n*n);
}
return 0;
}
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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